Notes

Unused Inodes

On a freshly formatted volume, inodes 0x0B to 0x0F are marked as
in use, but empty. Inodes 0x10 to 0x17 are marked as free and
not used. This doesn't change until the volume is under a lot
of stress.

When the $MFT becomes very fragmented it won't fit into one FILE
Record and an extension record is needed. If a new record was
simply allocated at the end of the $MFT then we encounter a
problem. The $DATA Attribute describing the location of the new
record is in the new record.

The new records are therefore allocated from inode 0x0F, onwards.
The $MFT is always a minimum of 16 FILE Records long, therefore
always exists. After inodes 0x0F to 0x17 are used up, higher,
unreserved, inodes are used.

This effect may not be limited to the $MFT, but more evidence is needed.

Other Information

For some reason $ObjId, $Quota, $Reparse and $UsnJrnl don't have
inode numbers below 24, like the rest of the Metadata files.

Also, the sequence number for each of the system files is always equal to
their mft record number and it is never modified.